COVER STORY , Sensitivity, and IOLs The importance of preoperatively assessing potential retinal acuity in the premium IOL patient.

BY JAY S. PEPOSE, MD, PHD

epending on its density and subtype, a the services associated with a deluxe lens raises the bar causes a variable reduction in both high-contrast considerably with respect to the results of surgery. It is (ie, spatial resolution) and contrast therefore particularly important to assess patients’ retinal Dsensitivity. Reduced contrast sensitivity, in part function preoperatively and identify those with associated due to forward light scatter, is particularly problematic for comorbid retinal conditions such as premacular fibrosis the patient. It blurs all lines of the eye chart rather than just and epiretinal membranes, , diabetic the lower lines as patients experience optical blur from an retinopathy, , or optic neuropathies that can uncorrected refractive error (Figure 1). Although patients negatively impact the qualitative or quantitative visual may still be able to decipher black letters against a backlit outcome of cataract surgery with a premium IOL. white background in the office, in the real world, they view This valuable information allows the surgeon to obtain a objects composed of a wide range of spatial frequencies and more accurate informed consent about the planned proce- illumination. Cataract patients with low contrast sensitivity dure and its risks, benefits, and likely outcome. More pre- function may have difficulty discerning facial expressions, cise informed consent helps to avoid a disappointing post- seeing the edge of a curb, pouring liquids into a cup, reading operative surprise. Patients with significant comorbid reti- in dim light, driving at dusk, and perceiving road hazards in a timely fashion. Contrast sensitivity involves both optical and neurological processing and generally decreases with age. A number of ocular conditions besides cataract may reduce contrast sen- sitivity and/or high-contrast visual acuity. Broadly, these include maculopathies, retinal degenerations, optic neu- ropathies, and glaucoma, any of which can coexist with cataracts. An important challenge to the ophthalmologist, therefore, is to preoperatively diagnose these comorbidities and to counsel cataract patients on their potential retinal acuity, postoperative visual prognosis, and appropriate IOL options.

WHY ASSESS RETINAL ACUITY PREOPERATIVELY? Patients considering a premium IOL have high expecta- Figure 1. Cataracts can result in a loss of both high-contrast tions of postoperative uncorrected acuity at more than visual acuity and contrast sensitivity, with distortion of the one focal plane. The substantial fee the patient pays for entire eye chart.

58 I CATARACT & REFRACTIVE SURGERY TODAY I MARCH 2009 COVER STORY

pathology or optic neuropathy. Surgeons should also exam- ine the peripheral , especially in high myopes who are at higher risk for retinal detachment. Although optical coherence tomography and fluorescein angiography as well as a referral to a retinal specialist may be appropriate for patients in whom pathology is identified, the anatomic appearance of the lesion often does not directly correspond with retinal function. For example, a gossamer-thin epireti- nal membrane seen on ophthalmoscopy, confirmed by optical coherence tomography, with no fluorescein findings, could still have a negative impact on visual function postop- eratively in a patient desiring a multifocal or accommodat- ing IOL. A patient with what appears to be significant dry macular degeneration, however, might have greater visual potential than the surgeon anticipates based upon appear- ance alone. Figure 2. The Retinal Acuity Meter is portable and light- weight, and it allows testing in less than 1 minute. METHODS OF ASSESSMENT Several tests have have been developed to predict nal or optic nerve pathology that inherently diminishes postoperative visual acuity. Pinhole testing, although contrast sensitivity may not be suitable candidates for mul- useful in practice by placing the eye at an almost uni- tifocal IOLs, which may decrease contrast sensitivity com- versal depth of focus and reducing optical aberrations, pared with aspheric monofocal IOLs. This loss of contrast has a disadvantage of reduced light because its small may relate to the splitting of light energy between multiple aperture limits retinal illumination. foci or the loss of light energy to higher diffractive orders. Clinical interferometry is based upon interference pat- The effect could be particularly troublesome in patients terns forming a series of black and white lines on the retina. whose optic nerve or macular function is already compro- The distance between these lines is used to define potential mised. In addition, there has been a report of a retinal sur- visual acuity. Unfortunately, there is a tendency to overesti- geon having impaired stereoscopic visualization intraopera- mate retinal potential with this method in eyes with concur- tively when performing an epiretinal membrane peeling in rent cataract and maculopathy, because the large a patient who had an acrylic multifocal IOL, despite a clear targets (in contrast to Snellen letters) can be effectively dis- view of the macula.1 Furthermore, there have been earlier cerned by portions of the retina outside the macula. reports of difficulty in performing vitreoretinal surgery in The Potential Acuity Meter (Marco Ophthalmics, patients with an Array silicone multi- Jacksonville, FL) projects a Snellen focal IOL.2 Implanting an accommo- chart in a small beam of light dating lens would raise fewer con- through the less opaque area of the cerns about decreased contrast sensi- lens onto the retina. It is more effec- tivity in eyes with retinal pathology tive than a pinhole or interferometer that might require vitreous surgery. due to its enhanced retinal illumina- Some fogging under air or silicone oil tion and the use of Snellen letters, with silicone IOLs, however, could respectively. The meter’s use is often affect visualization intraoperatively or cumbersome, however, because the result in residual oil’s beading against doctor or a technician must align the posterior aspect of the IOL after the letters and adjust the position of the oil’s removal, if there is a patent the patient’s head. Additionally, the capsulotomy. predictability of the Potential Acuity There is no substitute for a detailed Meter has been erratic in cases of history and retinal examination in dense media opacity, maculopathy, these patients. In addition, surgeons Figure 3. The panoramic pinhole option and/or advanced glaucoma.2-6 need to assess the patient’s macula clips onto the Retinal Acuity Meter trial In my practice, we routinely utilize and optic nerve with a 90.00 D or frame and has a series of seven viewing the Retinal Acuity Meter (AMA 78.00 D lens to identify macular apertures. , Inc., Miami, FL) to help us

MARCH 2009 I CATARACT & REFRACTIVE SURGERY TODAY I 59 COVER STORY

greater predictive accuracy with the Retinal Acuity Meter compared with the Potential Acuity Meter.5-7 The predict- ability of these tests, however, may vary with specific forms of macular comorbidity. Although no test of retinal function, including the Retinal Acuity Meter, has 100% specificity and sensitivity, in my practice, however, my colleagues and I have favored this device over others for reasons in addition to its accuracy. First, the test is easy to administer for both the patient and the technician. Unlike with the Potential Acuity Meter, chin- rest-eye alignment is not necessary, making it easier for patients with neck or back disease to undergo testing. The patient’s head does not move up and down on the chinrest Figure 4. The panoramic pinhole feature allows the patient to when he vocalizes responses, movement that could affect appreciate the potential visual improvement that may result the test’s accuracy. Another plus, the Retinal Acuity Meter is from clearing the optical media. small, lightweight, and battery operated with a calibrated light source. It fits inside a lab coat pocket, so it is readily assess patients’ potential visual function (Figure 2). The unit available for use in any room or examining lane without also helps us to identify patients with comorbid retinal or special setup. The test can be performed in less than 1 optic nerve pathology that may not be detected by history minute. A new accessory to the Retinal Acuity Meter is a and inspection alone, particularly in eyes with cloudy media. panoramic pinhole (Figure 3), which gives the patient a The Retinal Acuity Meter consists of an illuminated reading simultaneous visual comparison of his currently obscured card and a 16-inch retractable tape measure. The latter vision and his potential vision (Figure 4). This effect is pro- ensures that the card is held exactly 16 inches from the duced by views inside and outside the pinholes when a patient so that the target letters will subtend the appropri- cataract or other opacity is present in the eye.3 ate number of degrees of arc on the retina. The patient wears a trial frame over his distance cor- IN SUMMARY rection or glasses, which allows the insertion of Overall, I have found the Retinal Acuity Meter an opaque disc with eight pinholes, and a flip- to be a practical, affordable, and accurate tool for down +2.50 D lens available for a reading add. rapidly assessing retinal function and potential The illuminated viewing window in the device postoperative visual performance in patients displays single lines, and the target can be rotat- with 20/100 or better preoperative visual acuity. ed to present optotypes corresponding to The unit is not reliable for patients with a BSCVA between 20/200 and 20/20 visual acuity. of 20/200 or worse. The meter permits a detailed The effectiveness of the Retinal Acuity Meter is evaluation of macular function to correlate with based on three optical principles: visual angle cal- structural observations, provides important ibrated to testing at a fixed reading distance, information that assists in surgical counseling, bright illumination (16 times the brightness of a and allows me to deliver better care to my standard reading card), and pinhole effect, which cataract patients. If used routinely in patients decreases ocular aberrations and enlarges the with early-onset cataract, a sudden decrease in depth of field by obscuring unfocused rays of the Retinal Acuity Meter’s measurement may light. An evaluation of the image through all portend the onset of an unrelated comorbid dis- eight pinholes allows patients to select their opti- ease and a need for further evaluation. mal visual axis. They then align the image, pin- A Brightness Acuity Meter (AMA Optics, hole, least cloudy media pathway, and best reti- Figure 5. The Inc.) is lightweight portable. The device can per- nal region, thereby optimizing the assessment of Brightness Acuity form glare testing in conjunction with the potential retinal acuity. In contrast, with the Meter works in Retinal Acuity Meter modified with a calibrated Potential Acuity Meter, the examiner, rather than conjunction with light filter to reduce the reading window to the patient, aligns the image and chooses the the Retinal Acuity 85 cd/m2 (Figure 5). The Brightness Acuity ocular axis that appears to allow the target beam Meter to assess the Meter is a handheld device for measuring the to project through the least dense lenticular functional impact effects of glare on visual acuity. As stipulated by opacity. A number of studies demonstrate of glare. current Medicare guidelines, one indication for

60 I CATARACT & REFRACTIVE SURGERY TODAY I MARCH 2009 cataract extraction includes the uti- lization of a glare component that re- duces visual acuity to less than 20/40. The Brightness Acuity Meter also serves as a light source for the macu- lar photostress test, which can detect subtle forms of macular dysfunction. AMA Optics is also developing a unit that utilizes contrast sensitivity testing gradients. The Contrast Acuity Meter is a portable, back- illuminated, contrast sensitivity meas- urement system designed to evaluate visual function relative to changes in contrast under mesopic and photopic conditions with and without glare. The unit follows the model of the Regan chart optotype with contrast ratios from 96% to 4%, and it can be used with the Brightness Acuity Meter or another calibrated source of glare. ■

Jay S. Pepose, MD, PhD, is a professor of clinical oph- thalmology and visual sci- ences, Washington University School of Medicine, and di- rector, Pepose Vision Institute, St. Louis. He is a consultant to Bausch & Lomb and Visiogen but acknowledged no financial interest in any of the products or companies mentioned herein. Dr. Pepose may be reached at (636) 728- 0111; [email protected].

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